RELATED APPLICATIONS
This application is related to co-pending commonly assigned or partially commonly assigned, application of Otsuki et al, Ser. No. 662,630, filed Oct. 19, 1984, application of Otsuki et al, Ser. No. 667,221, filed Nov. 22 1984, and application of Tsuru et al, Ser. No. unknown, filed Mar. 22, 1985 (corresponding Japanese application No. 59-57130).
This invention relates generally to hydraulic braking apparatus for vehicles of the kind using a pedal-operated master cylinder controlling a supply of hydraulic fluid under pressure to wheel brakes, and more particularly to such a hydraulic braking apparatus with an electronic control unit which is capable of preventing kickback of the brake pedal.
The pressure of the braking fluid in a hydraulic braking apparatus for vehicles has to be optimally controlled in receipt of instructions from a control unit so that effective and safe braking is performed for decelerating a vehicle irrespective of the state of the road surface. To this end various anti-skid braking apparatus or anti-skid control devices have hitherto been proposed. According to conventional anti-skid braking apparatus, when a fluid-pressure control valve disposed between a master cylinder and a wheel cylinder of the braking system is put in pressure-decreasing mode in accordance with an instruction from a control unit, the brake fluid is led from the wheel cylinder to a reservoir and the fluid is further fed back to a fluid supply conduit of the master cylinder by way of a pressurizing pump.
In such conventional anti-skid braking apparatus, when the vehicle is stopped during the condition where the brake fluid is stored in the reservoir after the pressure control of the fluid is started, the brake fluid stored in the reservoir at the time of end of the pressure control, is further pressurized by the fluid-pressurizing pump to be returned to the master cylinder since the fluid-pressure control valve has been put in pressure-increasing mode in receipt of an instruction signal from the control unit. As a result, the pressurized fluid in the master cylinder pushes back, via the piston of the master cylinder, the brake pedal, producing so called kickback which gives uncomfortable feeling to the foot of the vehicle driver.
In order to solve this problem, a technique of preventing the brake fluid from flowing into the master cylinder when vehicle is stopped, by providing an accumulator at the outlet of the fluid-pressurizing pump and a check valve in the fluid supply conduit was proposed. This technique is used in an anti-skid control apparatus disclosed in a Japanese patent provisional publication No. 56-142733. However, in this known anti-skid control apparatus, fluid pressure still remains in the wheel cylinder due to cracking pressure of the check valve at the time of releasing the brake.